Ink cartridge detector, ink jet printer incorporating the same and ink cartridge detected by the same

ABSTRACT

An ink cartridge is detachably mounted on a cartridge holder. At least one first reflector is provided in the cartridge holder. A reflective-type optical sensor includes a light emitter and a light receiver. The optical sensor is operable to form an optical path originated from the light emitter to the light receiver via the first reflector. A shading member is provided in the ink cartridge operable to shade the optical path when the ink cartridge is mounted on the cartridge holder. A second reflector is provided in the ink cartridge. The second reflector reflects light emitted from the light emitter and varies an intensity thereof in accordance with an ink amount remaining in the ink cartridge.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to an ink cartridge detectoroperable to detect whether or not an ink cartridge is properly mountedon a cartridge holder. The invention also relates to an ink jet printerprovided with the above mentioned ink cartridge detector, and to the inkcartridge to be employed in the above mentioned ink cartridge detector.

[0002] There has been widely used an ink jet printer of a type thatprints characters and images on a printing medium by discharging inkwhich is supplied from an ink tank onto the printing medium through aprint head. In the ink jet printer of this type, the ink tank of acartridge system (hereinafter referred to as an “ink cartridge”) hasbeen widely employed so as to facilitate supply of the ink.

[0003] In the above described ink jet printer, it has been required todetect an amount of remaining ink in the ink cartridge and a mountingcondition of the ink cartridge for the purpose of preventing defectiveprinting due to shortage of the remaining ink in the ink cartridge orincomplete mounting of the ink cartridge, or for the purpose of issuingan alarm indicating the shortage or the incomplete mounting. For thisreason, there have been proposed mechanisms for enabling the amount ofthe remaining ink and the incomplete mounting of the ink cartridge to bedetected by a single optical sensor of the reflective type (disclosed inJapanese Patent Publications Nos. 10-230616A and 9-174877A, forexample).

[0004] In the above described detectors, a light beam is emitted fromthe optical sensor onto two reflectors (prisms) which are provided in abottom of the ink cartridge, and the amount of the remaining ink and themounting condition are detected on the basis of amounts of reflectivelight beams received from the reflectors. Specifically, the reflectorfor detecting the amount of the remaining ink is transparent so thatreflectivity (intensity of reflected light) may vary according to theamount of the remaining ink, while the reflector for detecting themounting condition is mirror-finished so that the light can be reflectedirrespective of the amount of the remaining ink.

[0005] However, in the above described related-art ink jet printer,there have been such problems as described below.

[0006] i) It has been necessary for the ink cartridge to be providedwith two reflectors which are formed of separate members, and hence, thenumber of components and production steps are increased, creating a highcost for the ink cartridge.

[0007] ii) Because the reflectors of the ink cartridge are exposedinside the printer even when a printing operation is performed, therehas been such a possibility that spots such as ink splashed during theprinting operation might adhere to the reflectors to make the detectionby the optical sensor unstable.

[0008] iii) When the optical sensor has received the reflective light,it is decided that the ink cartridge has been properly mounted.Therefore, when the optical sensor has received an exterior turbulentlight, it has been liable to be decided that the ink cartridge has beenproperly mounted, even though the ink cartridge has not yet been mountedAs such, the printing operation might be commenced without propermounting of the ink cartridge.

SUMMARY OF THE INVENTION

[0009] It is an object of the invention to provide an ink cartridgedetector, in which necessity for providing an ink cartridge with areflector for detecting the mounting condition can be eliminatedalthough the mounting condition of the ink cartridge is detected by anoptical sensor of reflective type, whereby not only reduction of costfor the ink cartridge can be attained, but also an erroneous recognitionof the mounting condition due to soils or ink splash on the reflector oran exterior turbulent light can be prevented.

[0010] It is also an object of the invention to provide an ink jetprinter incorporating such an ink cartridge detector, and an inkcartridge detected by such an ink cartridge detector.

[0011] In order to achieve the above objects, according to theinvention, there is provided an ink cartridge detector, comprising:

[0012] an ink cartridge;

[0013] a cartridge holder, on which the ink cartridge is detachablymounted;

[0014] at least one first reflector, provided in the cartridge holder;

[0015] a reflective-type optical sensor, including a light emitter and alight receiver, the optical sensor operable to form an optical pathoriginated from the light emitter to the light receiver via the firstreflector; and

[0016] a shading member, provided in the ink cartridge operable to shadethe optical path when the ink cartridge is mounted on the cartridgeholder.

[0017] The first reflector may be integrally fixed on a bottom portionof the cartridge holder. In such a configuration, not only the structurecan be simplified, but also reliability of detecting the mountingcondition of the ink cartridge can be enhanced, in comparison with acase where the reflector is provided as a movable member.

[0018] Further, the shading member may be integrally formed with the inkcartridge at a lower portion thereof (a downstream portion with regardto an inserting direction of the ink cartridge with respect to thecartridge holder). In such a configuration, the number of components andproduction steps of the ink cartridge can be reduced.

[0019] The ink cartridge may be formed with a recess which covers thefirst reflector when the ink cartridge is mounted on the cartridgeholder, so that at least one of side walls forming the recess serves asthe shading member. In such a configuration, because the first reflectoris covered when the ink cartridge has been mounted, soils or ink splashon the first reflector caused by a printing operation can be reliablyprevented.

[0020] The shading member may not shade the optical path when the inkcartridge is provisionally mounted on the cartridge holder. In such aconfiguration, such an inconvenience that the printing operation isconducted in a provisionally mounted state of the ink cartridge can beavoided.

[0021] The ink cartridge detector may further comprise a firstengagement member provided in the ink cartridge, and a second engagementmember provided in the cartridge holder. The first engagement member maycome into contact with the second engagement member such that the inkcartridge is retained at a first position in which the shading memberdoes not shade the optical path. In addition, the first engagementmember may engage with the second engagement member such that the inkcartridge is retained at a second position in which the shading membershades the optical path.

[0022] In one embodiment, the first engagement member is provided as aconvex portion formed on the ink cartridge, the second engagement memberis provided in a free end portion of an elastic member which issupported by the cartridge holder in a cantilevered manner; the secondengagement member is a V-shaped member including a first slope portionand a second slope portion so as to convex toward the ink cartridge; theconvex portion is brought into contact with the first slope portion whenthe ink cartridge is retained at the first position; and the convexpotion is retained by the second slope portion when the ink cartridge isretained at the second position.

[0023] Preferably, the optical sensor and the cartridge holder aremovable relative to each other. Here, it is preferable that a pluralityof first reflectors are arranged in a direction of relative movementbetween the optical sensor and the cartridge holder. In such aconfiguration, it is possible to detect the mounting conditions of aplurality of the ink cartridges by the same optical sensor.

[0024] Also, the ink cartridge detector may further comprise a secondreflector, provided in the ink cartridge, which reflects light emittedfrom the light emitter and varies an intensity thereof in accordancewith an ink amount remaining in the ink cartridge. Here, the secondreflector may be operable to form a part of an optical path originatedfrom the light emitter to the light receiver, when the ink cartridge ismounted on the cartridge holder. In such a configuration, it is possibleto detect both the mounting condition of the ink cartridge and theamount of the remaining ink by the same optical sensor.

[0025] According to the invention, there is also provided an ink jetprinter comprising the above ink cartridge detector.

[0026] Further, according to the invention, there is also provided anink cartridge, operable to be detachably attached to a cartridge holderprovided with a first reflector capable of forming a part of an opticalpath originated from a light emitter of an external optical sensor to alight receiver of the optical sensor, the ink cartridge comprising:

[0027] an ink reservoir, storing ink therein,

[0028] a second reflector, which reflects light emitted from the lightemitter and varies an intensity thereof in accordance with an ink amountremaining in the ink reservoir, the second reflector operable to form apart of an optical path originated from the light emitter to the lightreceiver; and

[0029] a shading member, which shades the optical path, which has beenformed by the first reflector and the optical sensor, when the inkcartridge is mounted on the cartridge holder.

[0030] Preferably, the shading member shades the first reflector fromthe light emitted from the light emitter, when the ink cartridge ismounted on the cartridge holder.

[0031] Here, a recess may be formed so as to cover the first reflectorwhen the ink cartridge is mounted on the cartridge holder, so that atleast one of side walls forming the recess serves as the shading member.The recess may be shaped as to surround an outer periphery of the firstreflector.

[0032] Also, it is preferable that the recess is formed on a faceopposing to the cartridge holder.

[0033] The ink cartridge may further comprise a first engagement member.In one embodiment, the first engagement member comes into contact with asecond engagement member provided in the cartridge holder, such that theink cartridge is retained at a first position in which the shadingmember does not shade the optical path. The first engagement memberengages with the second engagement member such that the ink cartridge isretained at a second position in which the shading member shades theoptical path.

[0034] Preferably, the second reflector and the shading member arejuxtaposed in a direction in which the cartridge holder and the opticalsensor are to be moved relative to each other.

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The above objects and advantages of the present invention willbecome more apparent by describing in detail preferred exemplaryembodiments thereof with reference to the accompanying drawings,wherein:

[0036]FIG. 1 is a side view schematically showing an interior structureof a printer;

[0037]FIG. 2 is a plan view schematically showing the interior structureof the printer;

[0038]FIG. 3 is a perspective view of a carriage on which a print headis mounted;

[0039]FIG. 4 is a front view of an ink supply section showing a state inwhich ink cartridges are not mounted.

[0040]FIG. 5 is a front view of the ink supply section showing a statein which the ink cartridges are mounted;

[0041]FIG. 6 is a perspective view of the ink supply section showing thestate in which the ink cartridges are not mounted;

[0042]FIG. 7 is a perspective view of the ink supply section showing thestate in which the ink cartridges are mounted;

[0043]FIG. 8 is a perspective view of the ink cartridge as viewed from abottom thereof;

[0044]FIGS. 9A to 9C are explanatory views showing detection of mountingcondition and detection of an amount of remaining ink;

[0045]FIG. 10 is a sectional view of the ink supply section taken alonga line X-X in FIG. 7, showing a state where the ink cartridge isplenarily mounted; and

[0046]FIG. 11 is a sectional view of the ink supply section taken alonga line Y-Y in FIG. 7, showing a state where the ink cartridge isprovisionally mounted

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0047] One embodiment of the invention will be described referring tothe accompanying drawings. As shown in FIG. 1, an inlet 11 for insertingpaper P by hand is provided on a front face of a printer 10. An outlet12 for discharging the paper P after printing is provided on an upperface of the printer 10. Inside the printer 10, there is formed a paperfeeding path 13 in a V-shape in a side view extending from the inlet 11to the outlet 12, and a paper feeding roller unit 14 and a print head 15are arranged on the paper feeding path 13. The paper feeding roller unit14 includes a paper feeding roller 16 and a paper holding roller 17which are opposed to each other on both sides of the paper feeding path13, and adapted to clamp and transport the paper P in accordance withdriving rotation of the paper feeding roller 16.

[0048] The print head 15 is mounted on a carriage 18 which reciprocatesin a lateral direction of the paper feeding path 13 (in a direction fromthe left to the right in FIG. 2), and adapted to perform dot matrixprinting on the paper P. The position of the paper P is regulated by aplaten 19. The printing system of the print head 15 is an ink jet systemin which characters or images are printed on the paper P by dischargingink, and the ink used for printing is supplied to the print head 15 froman ink supply section 20 which is provided in a rear area of the printer10.

[0049] The carriage 18 is supported by a pair of front and rear guideshafts 21, 22 so as to move from the left to the right, and is forciblymoved in accordance with driving motion of a carriage driving mechanism23. The carriage driving mechanism 23 includes a cam shaft 24 which isarranged below the front guide shaft 21 in parallel thereto, and acarriage motor 26 for actuating the cam shaft 24 to rotate by way of areduction gear train 25 (FIG. 2). On an outer peripheral face of the camshaft 24, there is formed a cam groove in a spiral shape (not shown),with which a cam follower 27 extending from the carriage 18 is adaptedto be engaged. When the cam shaft 24 is rotated in accordance with thedriving motion of the carriage motor 26, the cam follower 27 is shiftedin an axial direction with spiral shifting action of the cam groove. Inthis manner, it will be possible to reciprocate the carriage 18 from theleft to the right in accordance with normal and reverse drives of thecarriage motor 26.

[0050] As shown in FIG. 3, the print head 15 is mounted on an upper partof the carriage 18. A flat cable 28 and ink tubes 29 having flexibilityare drawn from a side area of the print head 15, and the ink is suppliedto the print head 15 from the ink supply section 20 by way of the inktubes 29. The carriage 18 has a sensor mounting part 18 a which isextended downwardly from its rear part, and an optical sensor 30 of areflective type which includes a light emitting element 30 a foremitting a light beam to the rear and a light receiving element 30 b forreceiving a reflective light beam is attached to a back face of thesensor mounting part 18 a.

[0051] As shown in FIG. 4, the ink supply section 20 includes acartridge holder 31 which is provided in a rear area inside the printer10, and two ink cartridges 32A, 32B which are detachably mounted on thecartridge holder 31 from the above. As shown in FIG. 8, an ink reservoir34A is partitioned inside the ink cartridge 32A to store secondary ink(for example, colored ink such as cyan, magenta, yellow, red, green,blue). The secondary ink is appropriately discharged from an ink outlet33A formed in a bottom of the ink cartridge 32A. A waste ink reservoir36 is also partitioned inside the ink cartridge 32A to store waste inksupplied from a recovery inlet 35 formed in the bottom. When the inkcartridge 32A has been mounted at a predetermined (specific) position onthe cartridge holder 31, the ink outlet 33A and the recovery inlet 35are communicated with connecting ports 37A, 38 which are formed in abottom of the cartridge holder 31, thus permitting supply of thesecondary ink and recovery of the waste ink.

[0052] On the other hand, inside the ink cartridge 32B, there arepartitioned an ink reservoir 34B which stores primary ink (for example,black ink) and appropriately discharges the primary ink from an inkoutlet 33B in a bottom of the ink cartridge 32B. When the ink cartridge32B has been mounted at a predetermined (specific) position on thecartridge holder 31, the ink outlet 33B is communicated with aconnecting port 37B which is formed in the bottom of the cartridgeholder 31, thus permitting supply of the primary ink.

[0053] The ink cartridges 32A, 32B are arranged in a row along a movingdirection of the carriage 18 (the optical sensor 30). The ink cartridges32A, 328 are respectively provided, at positions opposed to a movingpath L (see FIG. 5) of the optical sensor 30 on their front faces, withreflectors (reflectors for detecting an amount of remaining ink) 39A,39B in a shape of prism having transparency. The reflectors 39A, 39Bhave a shape of a right triangle prism, and two prism reflective facesS1, S2 which are at a right angle with respect to each other areprotruded into the ink reservoirs 34A, 34B. As shown in FIG. 9B, whenthe optical sensor 30 is moved to a position opposed to the reflector39A and a light is emitted thereto, the emitted light is reflected atthe prism reflective faces S1, S2 sequentially while passing interiorsof the reflector 39A, and received by the light receiving element 30 b.When the optical sensor 30 is moved to a position opposed to thereflector 39B and a light is emitted thereto, the emitted light isreflected at the prism reflective faces S1, S2 sequentially whilepassing interiors of the reflector 398, and received by the lightreceiving element 30 b.

[0054] Reflectivity (refraction index) of the prism reflective faces S1,S2 is low in the case where levels of the remaining ink in the inkreservoirs 34A, 34B are higher than the prism reflective faces S1, S2,and is high in the case where the levels of the remaining ink are lowerthan the prism reflective faces S1, S2. In short, in a state where theprism reflective faces S1, S2 are in contact with the ink as shown inFIG. 9A, an emitted light beam of the optical sensor 30 is absorbed bythe ink to have a low reflectivity (the intensity of reflected light ismade low), and in a state where the prism reflective faces S1, S2 are incontact with air as shown in FIG. 9B, the light beam is not absorbed bythe ink to have a high reflectivity (the intensity of reflected light ismade high). In this manner, it will be possible to detect the amount ofthe remaining ink (presence or absence of the ink at the predeterminedlevel) in the ink cartridges 32A, 32B on the basis of a value detectedby the light receiving element 30 b of the optical sensor 30.

[0055] As shown in FIGS. 4 and 6, on the bottom of the cartridge holder31, two reflectors (reflectors for detecting mounting condition) 40A,40B are fixed in a row along the moving direction of the carriage 18(the moving path L of the optical sensor 30), in an upwardly protrudingposture. Each of the reflectors 40A, 40B has a prism part 40 a in ashape of a right triangle prism, and reflective light paths of theoptical sensor 30 are formed by two prism reflective faces S3, S4 whichare at a right angle with respect to each other, in the same manner asthe reflectors 39A, 39B for detecting the amount of the remaining ink.On the other hand, recesses (hollowed parts) 41A, 41B are integrallyformed in respective lower portions of the ink cartridges 32A, 32B. Whenthe ink cartridges 32A, 32B have been mounted at the predeterminedpositions of the cartridge holder 31, the reflectors 40A, 40B areinserted into the recesses 41A, 41B, and the surroundings are covered.On this occasion, shield parts 42A, 42B which are integrally formed onone side faces of the recesses 41A, 41B (wall portions opposed to theoptical sensor) are interposed between the optical sensor 30 and thereflectors 40A, 40B, so as to shield light paths (irradiation paths andreflective paths) between the optical sensor 30 and the reflectors 40A,40B.

[0056] As shown in FIGS. 4 and 9C, in the state where the ink cartridges32A, 32B are not mounted on the cartridge holder 31, the reflectors 40A,40B are exposed. When the optical sensor 30 is moved to a positionopposed to the reflector 40A in this state, the emitted light issequentially reflected at the reflective faces S3, S4 while passing theinterior of the reflector 40A, and will enter the light receivingelement 30 b. When the optical sensor 30 is moved to a position opposedto the reflector 40B in this state, the emitted light is sequentiallyreflected at the reflective faces S3, S4 while passing the interior ofthe reflector 40B, and will enter the light receiving element 30 b. Onthe other hand, as shown in FIGS. 9A and 9B, in the state where the inkcartridges 32A, 32B have been mounted on the cartridge holder 31, frontareas of the reflectors 40A, 40B are covered with the shield parts 42A,42B. When the optical sensor 30 is moved to the position opposed to thereflector 40A in this state, the emitted light is shielded by the shieldpart 42A, and will not reach the reflector 40A nor the light receivingelement 30 b of the optical sensor 30. When the optical sensor 30 ismoved to the position opposed to the reflector 40B in this state, theemitted light is shielded by the shield part 42B, and will not reach thereflector 40B nor the light receiving element 30 b of the optical sensor30.

[0057] In this manner, it is possible to detect the mounting conditionof the ink cartridges 32A, 32B by the optical sensor 30, withoutproviding the ink cartridges 32A, 32B with the reflectors for detectingthe mounting condition. Moreover, in the state where the ink cartridges32A, 32B are not mounted on the cartridge holder 31 as described above,since the light receiving element 30 b is always subjected to the lightemission, an exterior turbulent light will not influence detectionresults of the mounting condition of the ink cartridges 32A, 32B, eventhough the exterior turbulent light is emitted to the light receivingelement 30 b. Further, in the state where the ink cartridges 32A, 32Bhave been mounted on the cartridge holder 31, since the reflectors 40A,40B are covered with the recesses 41A, 41B, the ink will not adhere tothe reflectors 40A, 40B, even though the ink is splashed during theprinting operation. As a result, it is possible to prevent an erroneousdetection caused by ink adhering to the reflectors 40A, 40B.

[0058]FIG. 10 is a sectional view of the ink supply section taken alonga line X-X in FIG. 7, showing a state where the ink cartridge isplenarily mounted, and FIG. 11 is a sectional view of the ink supplysection taken along a line Y-Y in FIG. 7, showing a state where the inkcartridge has been provisionally mounted. As shown in these drawings,there are provided, in a rear part of the cartridge holder 31, two lockplates 43A, 438 in an upright manner. The lock plates 43A, 43B areelastic plate members formed with V-shaped locking portions 44A, 44B intheir upper end portions. When the ink cartridges 32A, 328 have beenmounted on the cartridge holder 31 from above, convex portions 45A, 45Bprojected from back faces of the ink cartridges 32A, 32B lie on the lockportions 44A, 44B of the lock plates 43A, 43B, as shown in FIG. 11, tohold the ink cartridges 32A, 32B in a provisionally mounted state. Onthis occasion, the shield parts 42A, 42B of the ink cartridges 32A, 32Bare located above the prism parts 40 a of the reflectors 40A, 40B, andthe light paths between the optical sensor 30 and the reflectors 40A,40B will not be shielded.

[0059] Further, in the above described provisionally mounted state, whenthe ink cartridges 32A, 32B are pushed downward, the lock plates 43A,43B are pressed by the convex portions 45A, 45B to be tilted so as toonce retreat backward, and then, ride over the convex portions 45A, 45 bto be tilted so as to be returned forward. After the lock plates 43A,43B have been tilted to be returned, the locking portions 44A, 44B areengaged with upper parts of the convex portions 45A. 45B as shown inFIG. 10, and the ink cartridges 32A, 32B are held (locked) in theirmounting positions. On this occasion, the shield parts 42A, 42B of theink cartridges 32A, 32B are interposed between the prism parts 40 a ofthe reflectors 40A, 40B and the optical sensor 30 to shield the lightpath of the optical sensor 30.

[0060] As described above, according to this embodiment, the printer 10is constructed by including the optical sensor 30 of a reflective typewhich projects the light to the cartridge holder 31 to detect themounting conditions of the ink cartridges 32A, 32B on the basis of thereflective light, the reflectors 40A, 40B which are provided on thecartridge holder 31 to form the reflective light path of the opticalsensor 30, and the shield parts 42A, 42B which are provided in the inkcartridges 32A, 32B, and adapted to shield the light path of the opticalsensor 30 when the ink cartridges 32A, 32B have been mounted on thecartridge holder 31. In short, although the mounting condition of theink cartridges 32A, 32B is detected by the optical sensor 30 of thereflective type, necessity for providing the ink cartridges 32A, 32Bwith the reflectors for detecting the mounting condition can beeliminated. Therefore, not only reduction of the cost for the inkcartridges 32A, 32B can be attained, but also, an erroneous recognitionof the mounting condition due to soils such as ink splash on thereflectors or an exterior turbulent light can be prevented.

[0061] Moreover, because the reflectors 40A, 40B are fixed members whichare integrally provided in the bottom of the cartridge holder 31, ascompared with the reflectors 40A, 40B formed of movable members, notonly the structure can be simplified, but also reliability of detectingthe mounting condition can be enhanced.

[0062] Further, because the shield parts 42A, 42B are integrally formedin the lower parts of the ink cartridges 32A, 32B, the number of thecomponents and the production steps of the ink cartridges 32A, 32B canbe decreased.

[0063] Still further, because the ink cartridges 32A, 32B have therecesses 41A, 41B which cover the reflectors 40A, 40B when they havebeen mounted on the cartridge holder 31, and the shield parts 42A, 42Bare formed at the one side faces of the recesses 41A, 41B, thereflectors 40A, 40B can be protected when the ink cartridges have beenmounted, and defective detection due to soils such as ink splash ordamage of the reflectors 40A, 40B can be prevented.

[0064] Furthermore, the shield parts 42A, 42B will not shield the lightpath of the optical sensor 30 when the ink cartridges 32A, 32B areprovisionally mounted on the cartridge holder 31, and therefore,problems such as conducting the printing operation in the provisionallymounted state of the ink cartridges 32A, 32B can be avoided.

[0065] Still further, because the cartridge holder 31 and the opticalsensor 30 are relatively movable with respect to each other, it ispossible to detect the mounting conditions of a plurality of the inkcartridges 32A, 32B, and to detect the amount of the remaining ink inthe ink cartridges 32A, 32B by the same optical sensor 30.

[0066] Still further, the cartridge holder 31 is provided with aplurality of the reflectors 40A, 40B which are arranged in a row alongthe direction of the relative movement of the optical sensor 30 (alongthe line L shown in FIGS. 4 and 5), and accordingly, the same opticalsensor 30 can detect the mounting conditions of the plurality of the inkcartridges 32A, 328.

[0067] In addition, the ink cartridges 32A, 32B are provided with thereflectors 39A, 39B for detecting the amount of the remaining ink,enabling the amount of the remaining ink to be detected by the opticalsensor 30, and accordingly, the same optical sensor 30 can detect theamounts of the remaining ink as well as the mounting conditions of theink cartridges 32A, 328.

[0068] Although one of the embodiments according to the invention hasbeen described heretofore, the present invention is not limited to thosematters shown in the above described embodiment, but may include such ascope as those skilled in the art can make modification and applicationof the invention, on the basis of the description in the claims and inthe detailed description of the invention, and the well known art.

[0069] For example, although in the above described embodiment, theshield part is formed on one side face of the recess which is integrallyformed in the ink cartridge, the shield part may be in any shape,provided that it can shield the light path of the optical sensor 30 whenthe ink cartridge has been mounted on the cartridge holder. For example,the shield part may be formed in a hook-like shape (L-shape) on the oneside face of the ink cartridge.

[0070] Moreover, although in the above described embodiment, the inkcartridges are mounted on the printer body, the invention can berealized in the printer in which the ink cartridges are mounted on thecarriage. Specifically, by providing the reflectors on the cartridgeholder which is mounted on the carriage, and detecting them by theoptical sensor which is provided on the printer body, similar functionand advantageous effects to those in the above described embodiment canbe obtained.

[0071] According to the present invention as has been herein beforedescribed, although the mounting condition of the ink cartridge isdetected by the optical sensor of a reflective type, necessity forproviding the ink cartridge with the reflectors for detecting themounting condition is eliminated, and not only reduction of the cost forthe ink cartridge can be attained, but also, an erroneous recognition ofthe mounting condition due to soils such as ink splash on the reflectorsor an exterior turbulent light can be prevented.

What is claimed is:
 1. An ink cartridge detector, comprising: an inkcartridge; a cartridge holder, on which the ink cartridge is detachablymounted; at least one first reflector, provided in the cartridge holder;a reflective-type optical sensor, including a light emitter and a lightreceiver, the optical sensor operable to form an optical path originatedfrom the light emitter to the light receiver via the first reflector;and a shading member, provided in the ink cartridge operable to shadethe optical path when the ink cartridge is mounted on the cartridgeholder.
 2. The ink cartridge detector as set forth in claim 1, whereinthe first reflector is integrally fixed on a bottom portion of thecartridge holder.
 3. The ink cartridge detector as set forth in claim 1,wherein the shading member is integrally formed with the ink cartridgeat a downstream portion thereof with regard to an inserting direction ofthe ink cartridge with respect to the cartridge holder.
 4. The inkcartridge detector as set forth in claim 1, wherein the ink cartridge isformed with a recess which covers the first reflector when the inkcartridge is mounted on the cartridge holder, so that at least one ofside walls forming the recess serves as the shading member.
 5. The inkcartridge detector as set forth in claim 1, wherein the shading memberdoes not shade the optical path when the ink cartridge is provisionallymounted on the cartridge holder.
 6. The ink cartridge detector as setforth in claim 5, further comprising: a first engagement member,provided in the ink cartridge; and a second engagement member, providedin the cartridge holder, wherein: the first engagement member comes intocontact with the second engagement member such that the ink cartridge isretained at a first position in which the shading member does not shadethe optical path; and the first engagement member engages with thesecond engagement member such that the ink cartridge is retained at asecond position in which the shading member shades the optical path. 7.The ink cartridge detector as set forth in claim 6, wherein: the firstengagement member is provided as a convex portion formed on the inkcartridge; the second engagement member is provided in a free endportion of an elastic member which is supported by the cartridge holderin a cantilevered manner; the second engagement member is a V-shapedmember including a first slope portion and a second slope portion so asto convex toward the ink cartridge; the convex portion is brought intocontact with the first slope portion when the ink cartridge is retainedat the first position; and the convex potion is retained by the secondslope portion when the ink cartridge is retained at the second position.8. The ink cartridge detector as set forth in claim 1, wherein theoptical sensor and the cartridge holder are movable relative to eachother.
 9. The ink cartridge detector as set forth in claim 8, wherein aplurality of first reflectors are arranged in a direction of relativemovement between the optical sensor and the cartridge holder.
 10. Theink cartridge detector as set forth in claim 1, further comprising asecond reflector, provided in the ink cartridge, which reflects lightemitted from the light emitter and varies an intensity thereof inaccordance with an ink amount remaining in the ink cartridge.
 11. Theink cartridge detector as set forth in claim 10, wherein the secondreflector is operable to form a part of an optical path originated fromthe light emitter to the light receiver, when the ink cartridge ismounted on the cartridge holder.
 12. An ink jet printer comprising theink cartridge detector as set forth in claim
 1. 13. An ink cartridge,operable to be detachably attached to a cartridge holder provided with afirst reflector capable of forming a part of an optical path originatedfrom a light emitter of an external optical sensor to a light receiverof the optical sensor, the ink cartridge comprising: an ink reservoir,storing ink therein; a second reflector, which reflects light emittedfrom the light emitter and varies an intensity thereof in accordancewith an ink amount remaining in the ink reservoir, the second reflectoroperable to form a part of an optical path originated from the lightemitter to the light receiver; and a shading member, which shades theoptical path, which has been formed by the first reflector and theoptical sensor, when the ink cartridge is mounted on the cartridgeholder.
 14. The ink cartridge as set forth in claim 13, wherein theshading member shades the first reflector from the light emitted fromthe light emitter, when the ink cartridge is mounted on the cartridgeholder.
 15. The ink cartridge as set forth in claim 14, wherein a recessis formed so as to cover the first reflector when the ink cartridge ismounted on the cartridge holder, so that at least one of side wallsforming the recess serves as the shading member.
 16. The ink cartridgeas set forth in claim 15, wherein the recess is so shaped as to surroundan outer periphery of the first reflector.
 17. The ink cartridge as setforth in claim 15, wherein the recess is formed on a face opposing tothe cartridge holder.
 18. The ink cartridge as set forth in claim 13,further comprising a first engagement member, wherein: the firstengagement member comes into contact with a second engagement memberprovided in the cartridge holder, such that the ink cartridge isretained at a first position in which the shading member does not shadethe optical path; and the first engagement member engages with thesecond engagement member such that the ink cartridge is retained at asecond position in which the shading member shades the optical path. 19.The ink cartridge as set forth in claim 13, wherein the second reflectorand the shading member are juxtaposed in a direction in which thecartridge holder and the optical sensor are to be moved relative to eachother.